Question GPU Temps rise then black screen

[annkr]

Hi, I am having trouble with my gaming PC crashing. At first it started to switch off after the game getting laggy and then randomly switching off I have checked the temps and the usage. When its about to crash its 100% and around 105 degrees celcius CPU was around staying around 45 degrees and running around 50%.. Would it be a fault with the graphics card? I think i might of had overclocked it before it happens so i redownloaded msi afterburner but it wasnt overclocked. I know a bit about PCs but not THAT much. Also just to say the whole thing started when my thermal paste dried out, although i replaced it regularly, it still happens. I replaced it last night and its happening now. Should I be Looking at a new graphics card? I dont have much budget to buy one though.
ALSO
It doesnt crash on like normal stuff, just games. although while on yt and stuff its like 80 degrees.

I have a gt 630

 

[Lutfij]

Welcome to the forums, newcomer!

We're going to need a little more information. When posting a thread of troubleshooting nature, it's customary to include your full system's specs. Please list them like so:
CPU:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
Monitor:

include the age of the PSU apart from it's make and model.

the whole thing started when my thermal paste dried out
On the CPU or the GPU? If the GPU, did you make sure the pads weren't removed?

although i replaced it regularly
How often have you done so? Thermal Interface Material(TIM) shouldn't dry up on your GPU on a regular basis. If so, it means you have an improper mount or you're vaporizing your TIM taxing your GPU to breaking point.

 

[annkr]

CPU: i7 4790
Motherboard: idk
Ram: 2x4 gb ddr3 1600mhz
SSD/HDD: ssd is
HikVision E100 128GB SSD
hdd is SEAGATE ST500DM002
GPU:gt 630
PSU:i 450w
Chassis: Dell Precision T1700
OS: Windows 10
Monitor:HP EliteDisplay e231i